1) Field of the Invention
This invention relates to a novel monoglyceride lipase, its production process and an analytical method making use of the novel monoglyceride lipase, as well as an analytical method of the enzymatic activity of pancreatic lipase.
2) Description of the Related Art
The monoglyceride lipase, which has conventionally been known to exist in a wide range of organisms ranging from microorganisms to higher animals, is known to act not only on monoglyceride but also on diglyceride and triglyceride ["KOSO HANDBOOK (Enzyme Handbook)", page 424; published Dec. 1, 1982 by The Asakura Shoten K.K.]. As another monoglyceride lipase, is known that derived from certain microorganism strains of Staphyrococcus (Japanese Patent Laid-Open No. 42532/1980). This enzyme also acts as its substrate specificity on triglyceride in addition to monoglyceride and has the following physical and chemical properties. Its optimum pH is pH 11. As its optimum temperature, it shows high activity in a range of 37-50.degree. C., with the activity peak located around 37-40.degree. C., when "Ediol" (trade mark; coconut oil emulsion) is used as a substrate. Its isoelectric point is 2.56, while its molecular weight is about 174,000. Further, it is inactivated rapidly at 55.degree. C. and higher and its inactivation at 70.degree. C. takes place in 10 minutes. On the other hand, known analytical methods for the activity of lipase include turbidimetric method using of triolein emulsion, the colorimetric method using a synthetic substrate (Japanese Patent Laid-Open No. 254,197/1986), the titration method in which a liberated fatty acid is titrated, the enzymatic measurement method of a fatty acid formed by using 1,2-diglyceride, a natural substrate, in the form of a synthetic substrate (Japanese Patent Laid-Open Nos. 888/1983 and 91,898/1984), etc.
Since conventional monoglyceride lipases act not only monoglyceride but also diglyceride and triglyceride as mentioned above, they cannot be used, for example, for a method of measuring only monoglyceride liberated from a synthesized substrate in the measurement method of the activity of lipase. Further, the monoglyceride lipase from the microorganism strains of Staphyrococcus cannot be used either, because it also acts on triglyceride, its molecular weight and optimum pH are high, and it is unstable under heat.